Referring now to FIGS. 1 to 5, a conventional recliner device for a vehicle seat will be discussed hereinafter in order to facilitate understanding of the present invention. As shown in FIG. 1, the conventional recliner device generally includes first brackets 1 provided at both sides of a seat back B of the vehicle seat and extending downwardly from the both sides of the seat back B, and second brackets 2 provided at both sides of a seat cushion C of the vehicle seat and extending rearwardly from the both sides of the seat cushion C. As shown in FIG. 2, the first brackets 1 (only one first bracket 1 is shown in FIG. 2) pivotally connected to the second brackets 2 (only one second bracket 2 is shown in FIG. 2) by causing lower end portions of the first brackets 1 to be disposed on inner surfaces of rear end portions of the second brackets 2 and causing the lower end portions of the first brackets 1 to be coupled to the rear end portions of the second brackets 2 by means of supporting pins 3 (only one supporting pin 3 is shown in FIG. 2), so that the seat back B can be pivoted around the supporting pins 3 relative to the seat cushion C, that is, an attitude of the seat back B can be selectively changed to a vertically standing posture, a forwardly inclined posture or a rearwardly inclined posture.
As shown in FIGS. 3 to 5, the conventional recliner device further includes a locking pin 4 which penetrates one of the second brackets 2 so as to be axially movable, and extends towards a lower end edge of corresponding one of the first brackets 1. The lower end edge of the first bracket 1 is formed in a substantially semicircular shape and has three engaging notches 1a, 1b, 1c disposed at predetermined circumferential intervals around the supporting pin 3. An inner end portion 4a of the locking pin 4 is releasably engaged with any one of the engaging notches 1a-1c of the first bracket 1 by an action of a coil spring discussed hereinafter, whereby the seat back B can be selectively locked in the vertically standing posture, the forwardly inclined posture or the rearwardly inclined posture with respect to the seat cushion C. The conventional recliner device is disclosed in Japanese Patent Application Laid-Open No. Hei. 9-117339.
As shown in FIGS. 4 and 5, the locking pin 4 is provided with a circumferential flange 4b. A substantially cylindrical pin-holder 5 is fixed on an outer surface of the second bracket 2 and surrounds the locking pin 4. An outer end portion 4c of the locking pin 4 projects outwardly from the pin-holder 5. The pin-holder 5 has an inwardly facing circumferential flange portion 5a. The coil spring 6 briefly discussed above is mounted around the locking pin 4 and disposed between the circumferential flange 4b of the locking pin 4 and the inwardly facing circumferential flange portion 5a of the pin-holder 5. Due to an action of the coil spring 6, the locking pin 4 is always urged toward the first bracket 1 and the inner end portion 4a of the locking pin 4 is releasably engaged with any one of the notches 1a-1c of the first bracket 1. An operating knob 7 is movably mounted on the pin holder 5 and fastened to the outer end portion 4c of the locking pin 4 by a screw 8.
In the conventional recliner device, when the operating knob 7 is drawn against the action of the coil spring 6 by a person in such an axial direction as to be away from the first bracket 1 as indicated by an arrow in FIG. 5, the locking pin 4 is drawn in the same direction, whereby the locking pin 4 is disengaged from the one of the engaging notches 1a-1c with which the locking pin 4 has been engaged until now. Thus, the seat back is brought into a condition where the seat back is allowed to be pivoted relative to the seat cushion. However, in order that the locking pin 4 can be positively disengaged from the engaging notch against the action of the coil spring 6, the person must draw the operating knob 7 with a considerable pulling-force. Therefore, it is hard for physically weak persons such as aged persons and children to operate the operating knob.